Do you ever wonder why your heart races and you can’t think clearly when you’re afraid? Sure, you may not actually need to fear that skeleton in the haunted house or the White Walker streaming through the screen, but try telling that to your body’s fear response.
When you’re scared, even if it’s just from good old-fashioned Halloween fun or your favorite TV show, your brain sets off an elaborate and coordinated set of responses to help you stay safe, says Daniel Evans, Ph.D., a clinical psychologist who practices at the UW Neighborhood Northgate Clinic. Physical changes—from deep inside your brain all the way to the muscles in your legs—happen in seconds.
“They’re all evolutionarily-developed reflexes and happen quite quickly,” he says.
Fear starts in the brain
Most of us don’t have to think about breathing, digesting our food or making our heart beat. The autonomic nervous system takes care of these functions we think of as automatic. It is divided into two branches: the parasympathetic nervous system (the rest and digest system) and the sympathetic nervous system (the fight-or-flight system).
Fear kicks your fight-or-flight response into overdrive, Evans says. Your adrenal glands secrete adrenaline. Blood flow decreases to your brain’s frontal lobe, which is responsible for logical thinking and planning, and the deeper, more animalistic parts of your brain—including the amygdala—take over.
Like an animal trying to avoid being eaten by a predator, all of your body’s resources get diverted toward one goal: staying alive. Your heart rate and blood pressure increase, you breathe faster and your muscles tense up. Your pupils dilate so you can see the threat more clearly, says Evans.